Easy, quick, and delicious.
Set the oven to 375 degrees.
Peel and then thinly slice onion to make 1 C. Trim 1 lb. of sweet peppers and remove the core and seeds. Slice lengthwise.
In a large cast iron skillet, heat 3 T. olive oil. Saute the onion until soft, then add the peppers. Sprinkle with salt and pepper.
Meanwhile, thinly slice 2 lbs. of potatoes in rounds. When the peppers are soft, layer the potatoes on top of the onion/pepper mixture. Sprinkle salt over the potatoes.
Cover the pan and bake for 45 minutes or until the potatoes are tender. Grate 1/2 lb. sharp cheddar or manchego cheese over the casserole. Set the oven to low broil and then cook until the cheese is browned and bubbly.